Petroleum asphalt is used as a paving material, a roofing material, a waterproof material, and so on. Among these usages, demand for the paving material is the largest. In paving roads with heated asphalt, aggregates and asphalt are mixed and applied under heat. However, since nonpolar hydrophobic asphalt does not adhere sufficiently to hydrophilic aggregates, there is a potential problem in that asphalt peels from the aggregates through the interventional action of rainfall and ground water.
Thus, an improvement in the adhesiveness between the asphalt and the aggregates is a very important item for improving performance of the paved roads with heated asphalt; accordingly, many methods have been devised so far to improve the same.
For example, in JP-A No. 2001-2928, as a countermeasure for this, higher aliphatic polyalkylene polyamine and a salt of a modified polyolefin resin having a carboxyl group are used. However, although the adhesive property immediate after the addition to the heated asphalt can be improved, there is a problem in that the peeling prevention effect decreases after 4 to 7 days when preserved at a high temperature.
Furthermore, in JP-A No. 60-188462, it is described that a specific acidic organic phosphorous compound is effective in solving the problem mentioned above. However, though the adhesive property and the peeling effect are improved compared with other additives so far proposed, there is still room for improvement in the immediate result demanded in the market.
Recently there is a concern about the deterioration in qualities of asphalt and the aggregates. From the viewpoint of the effective utilization of resources, on the other hand, a recycling method of waste materials of pavement is proposed. However, in this case, as deteriorated asphalt is used, strong adhesion cannot be anticipated.
As just described, there is a tendency for increased demand for an improved asphalt for paving materials that uses the heated asphalt and the aggregates. However, a method that can solve the problems mentioned above and the performances demanded in market has not been developed yet.
Furthermore, in JP-A No. 9-157530, asphalt emulsion containing a gallic acid and/or gallic acid derivative is described. However, it is a technology relating to an asphalt emulsion system and has no relation with a system that uses heated asphalt containing no water.